This invention relates generally to the field of minimally invasive surgery, and in particular to a hand-held, bipolar laparoscopic device for electrical or mechanical cutting of biological tissue and for coagulation of the tissue.
Nearly every open and laparoscopic surgical procedure requires the cutting and sealing of vascularized tissue. To reduce or minimize bleeding of the tissue, conventional surgical scissors have begun to be replaced with electrically energized scissors in monopolar and bipolar configurations, each offering certain advantages and disadvantages. Monopolar refers to a configuration where a return electrode is coupled to a patient, typically in the form of a patch coupled to the patient's skin, so that only one active electrode need be carried on the surgical instrument. With the monopolar technique, a concentrated electrical current is delivered from the active electrode on the instrument to targeted tissue, causing coagulation that stops bleeding. The electricity then disperses and flows through the patient en route to the return electrode attached to the patient's skin. Bipolar refers to a configuration wherein the instrument carries both the active and return electrodes, delivering energy to tissue between the two electrodes.
Monopolar electrosurgical instruments facilitate several surgical functions, such as cutting tissue, coagulating tissue to stop bleeding, or concurrently cutting and coagulating tissue. The surgeon can apply a current whenever the conductive portion of the instrument is in electrical contact with the patient, permitting the surgeon to operate with monopolar instruments from many different angles. However, as stated above, monopolar electrosurgical instruments do have some drawbacks, especially when used for laparoscopic procedures.
During laparoscopic monopolar electrosurgery, the view of the surgical field is somewhat constricted. The surgeon operates from the exterior of the patient's body using remote instrumentation. The manipulation of instruments and tissue is based on magnified images that are relayed from a camera connected to a laparoscope and displayed on a monitor. The active electrode may be in close proximity to other conductive instruments and to tissue, and may result in stray electrical current being transmitted to unseen tissue off the extended shaft of the remote laparoscopic instruments, possibly leading to thermal injury to the patient.
Stray currents may cause patient injury outside the laparoscope's view via direct coupling, insulation failure, or capacitive coupling. Direct coupling occurs when the active electrode touches another metal instrument within the patient, such as in the abdomen, transferring energy to the second instrument and possibly injuring tissue with which it comes in contact.
Insulation failure occurs when the insulated shaft of the electrode, which is designed to protect against the release of stray electrical current, becomes compromised due to insulation breakdown. The breakdown along the unseen shaft of an activated electrode can allow electrical current to leak into surrounding non-targeted tissue, causing unobserved damage.
Capacitive coupling occurs when electrical current is induced from the active electrode to nearby conductive material, despite intact insulation. During electrosurgery, the charge on the active electrode switches from highly positive to highly negative at a very high frequency. The rapidly varying electrical field around the active electrode is only partially impeded by electrical insulation and creates stray electrical currents by alternately attracting and repelling ions in surrounding body tissue. The movement of electrically charged ions in capacitively coupled tissue can cause currents that can heat tissue sufficiently to produce a burn.
In comparison to monopolar surgical instruments, such as monopolar scissors, the electrical current in a bipolar arrangement is not required to travel long distances through the patient before returning to the return electrode, thereby greatly reducing the minute risk of accidental burns. Instead, a bipolar electrode arrangement applies electrical current only between two energized cutting blades which are closely spaced and always within the field of view of the surgeon. A bipolar arrangement also requires less electrical power than a monopolar arrangement because the electrical current disperses through a much smaller volume of tissue. More importantly, a bipolar arrangement eliminates the possibility of accidental burns through an insulation failure of the active shaft and greatly reduces the risk of direct coupling and capacitive coupling. However, bipolar instruments require the surgeon to carefully position the instrument to ensure that both the active and return electrodes are in electrical contact with the patient before applying a current. This may limit the range of motion and the angle from which the surgeon can effectively use the bipolar instrument.
There are several variations for placement of electrodes on electrosurgical scissors that allow electrical current to flow through the cut tissue. For example, the exterior surface of one shearing member can include an active electrode while the exterior surface of the other shearing member can include a return electrode. In this configuration, electrosurgical current can flow from the exterior surface of one blade, through the cut tissue, to the exterior surface of the other blade.
In another variation, each of the two shearing surfaces includes an active electrode, while each of the two exterior surfaces includes a return electrode, or vice versa. In this configuration, electrical current can flow from each shearing surface, through the cut tissue, to an exterior surface, or vice versa.
Apart from mechanical cutting, the practicality of monopolar scissors makes them more favorable to surgeons. Monopolar scissors not only permit a surgeon to coagulate tissue between the blades prior to cutting the tissue mechanically, but they also permit the surgeon to dissect thin connective tissue electrically by moving one blade in a sweep-like motion over the tissue. Monopolar scissors also permit electrosurgical coagulation of small blood vessels that are cut open during a mechanical cutting process. This is typically performed by energizing the tissue with the exterior surface of one of the scissor blades.
Conventional bipolar scissors also permit electrical coagulation and cutting of the tissue between the blades, but they do not allow for the common practice to utilize one blade for dissection of tissue by moving the blade in a sweep-like motion over the tissue. Conventional bipolar scissors also do not allow for simultaneous coagulation of tissue between the blades and surrounding tissue, or coagulating the tissue by energizing it with the exterior surface of one of the blades. This is due to the common approach to separate the high frequency (HF) coagulation and mechanical cutting action both spatially and functionally by arranging the active, electrically conductive, radio frequency (RF) electrodes on the outside of each electrically conductive blade, while being electrically insulated through insulators, such as ceramic or plastic.
One improved bipolar scissors includes blades having electrodes on the inner surface of each blade with the electrodes being connected to the same pole to avoid a short circuit between the mating inner faces of the blades. The outer surface of each of the blades includes at least two electrodes connected to opposite poles, meaning that at least one of the electrodes on the outer surface of each blade is connected to the same pole as the electrode on the inner surface of the blade. With these scissors, all of the electrodes are energized simultaneously and there are no means to have less than all of the electrodes energized when applying electrical current to the electrodes. In this manner, it is not possible to coagulate only the tissue between the blades. If an electrical current is applied while cutting the tissue, the surrounding tissue is also coagulated.